The invention relates to an apparatus for melting by vapor-phase treatment a solder that has been applied to an object.
An apparatus for melting by vapor-phase treatment a solder that has been applied to an object is disclosed in the German Patent No. 2,442,180. This apparatus has a vessel which contains a heat-transfer liquid. The vessel is provided with entry and exit ports through which the object that is to be treated can enter and leave, respectively. The heat-transfer liquid is heated at least to ebullition by electrical heating means disposed in this liquid. External heat sources, such as a hot-plate for example, can additionally be used. In the vessel there is produced a saturated vapor of the heat-transfer liquid which condenses in contact with the solder and the object that are to be treated. By the transfer of the latent heat of evaporation from the condensed vapor to the object, the solder is heated so that it melts on the object.
In such apparatus a liquid fluorocarbon is preferably used as the heat-transfer liquid. Heated vapor, which can reach the atmosphere through the entry and exit ports, is hazardous to health, so that the allowable amount of such vapor emission is increasingly limited by government regulations as well as by safety standards, in order to protect personnel operating or working near the apparatus. Such hazards, however, cannot be eliminated from the known apparatus because burn-through and resultant excessive overheating of the heat-transfer liquid cannot be completely prevented. Also, the incrustation of the heating elements disposed in the heat-transfer liquid cannot be completely prevented in the known apparatus.
The principal objectives of the invention are therefore to create an electrical heating system for apparatus for melting, by vapor-phase treatment, the solder applied to an object, which (1) will prevent the formation of toxic vapors from the heat-transfer liquid, (2) will permit a good input of heat to this liquid, and (3) will be easy to clean.